This invention relates to improved methods and apparatus to prompt patients with lung disease, and other subjects, into more physiologically appropriate breathing patterns by simple visual and auditory biofeedback means. Hilisman incorporates by reference his U.S. Pat. No. 3,991,304 which describes a sophisticated and complex visual biofeedback device suitable only for medical professional use. This present invention extends that concept into a simple portable device suitable for use under field operational conditions, with both visual and auditory biofeedback means suitable for individual subject use in a lower technical environment.
A wide variety of timing metronomes of both mechanical and electrical design have been well known in the music industry for many years. Almost all have been simple devices designed to give an auditory signal of equal periodicity and permitting only an overall rate adjustment. More modern electronic music metronome devices permit a wide spectrum of timing signals suitable for music timing and rhythm coordination needs, and some with visual prompting. This present invention relates to a timing device unique for medical needs wherein the overall rate and the relative timing of inspiration and expiration are adjustable, in essence therefore an xe2x80x9casynchronous metronomexe2x80x9d specific to medical respiratory needs.
In the course of using Hillsman""s advanced visual biofeedback training device, U.S. Pat. No. 3,991,304 it was discovered that native breathing patterns in diseased emphysema patients could be altered and that these altered breathing patterns were retained in part (Reference: A Biofeedback Method To Alter Breathing Patterns In COPD; Hilisman, D. and Lillington, G. A.; Third International Conference on Pulmonary Rehabilitation and Mechanical Ventilation; Mar. 12, 1991xe2x80x94Reference: A Visual Biofeedback Method To Define And Teach Breathing Patterns, and, Clinical Experience With A Visual Biofeedback Method In COPD Rehabilitation; Hillsman, D.; International Society for the Advancement of Respiratory Psychophysiology; Second Annual Meeting, Oct. 9, 1995, Biological Psychology, Vol. 43, Issue 3, Jun. 28, 1996, pages 261 and 243-244. In some unknown manner it is apparent these learned breathing patterns are being imprinted in the patient""s subconscious, and recalled and used with a variable degree of accuracy. Though it is usually easy to get patients to follow breathing pattern analogs using the sophisticated visual device, the problem of proper breathing patterns in the home environment remained. Furthermore, many patients would revert to their previous inefficient native breathing patterns under conditions of stress or with the passage of time. It was discovered with the patient blinded, a simple auditory signal to breathe in and out at the appropriate points in the breathing cycle was highly effective in prompting patients into an accurate reproduction of the breathing waveform analog. Thus the concept of the instant invention was created, to activate these learned breathing patterns in a more reliable and accurate manner by means of an auditory xe2x80x9cbeepxe2x80x9d (high pitched) and the beginning of inspiration and another xe2x80x9cbeepxe2x80x9d (low pitched) at the beginning of expiration. Further, it was considered desirable to use the familiar and soothing xe2x80x9ctick/tockxe2x80x9d sound of a grandfather clock as the auditory prompt as the preferred embodiment, though the concept could also be implemented with a variety of brief or continuous individual sounds or musical sounds or breath sounds of inspiration and expiration.
The physiologic theory underlying Emphysema and Asthma breathing patterns is discussed in U.S. Pat. No. 3,991,304 and in the references. Briefly, when suffering dyspnea it is natural for a patient to try and breathe faster, to inspire in a dominant manner, to breathe forcefully, and generally to shorten the time of expiration. Pulmonary mechanical reasons require such patients to breathe slower, to breathe gently, and to breathe dominantly focused on expiration and to prolong the time of expiration. If the patient does not breathe in this manner they exhibit the problem of so-called xe2x80x9cAir Trappingxe2x80x9d as it is inherently more difficult to exhale than to inhale, and particularly so with severe airway obstructive disease and Emphysema. This leads to so-called xe2x80x9cDynamic Hyperinflationxe2x80x9d (or Dynamic Overinflation) which places the chest wall and respiratory muscles in a position of mechanical disadvantage and therefore further acutely exacerbates the dyspnea sensation. Deflation of the overinflated chest is therefore critical in such patients.
It has been discovered that patients may be effectively taught to deflate their overinflated lungs with the visual biofeedback training system by showing them how to prolong their expiratory phase past the normal end point of the display by approximately 25% of the programmed expiratory time. Then, when told to breathe in, a reset button is activated that synchronizes the patient inspiration signal with a new prompting waveform. This overinflation corrective breathing pattern may be indicated in the portable prompting device by an override button which prolongs the expiratory phase by 25% while simultaneously giving a continuous visual and/or auditory signal and then resuming the usual prompting signals. The patient continues to press the override button for approximately five to ten breaths, and when again relatively comfortable releases the override button and resumes the normal breathing prompting program.
Hyperventilation Syndrome is a well recognized disease entity wherein so-called xe2x80x9cPanic Attacksxe2x80x9d lead to excessive breathing, which in turn causes the elimination of excessive and inappropriate amounts of carbon dioxide from the body. Carbon dioxide is a waste product of metabolism and intimately linked to the pH regulation of the body as the dominant volatile acidic component of metabolism. Thus, the excessive loss of this acidic component causes metabolic imbalance to the alkaline side of metabolism, and therefore the production of so-called Respiratory Alkalosis. Respiratory Alkalosis typically causes a wide spectrum of symptoms, including lightheadedness and tingling about the face and hands in mild cases. There may be progressive impairment of cognitive function and later severe disorientation and dizziness or even syncope, which would be a severe danger for subjects in hazardous work or recreational environments. Therefore there is a need for a simple device that can appropriately regulate excessive ventilation under a variety of sometimes hostile field operative conditions, including underwater diving conditions.
It is therefore one object of the present invention to provide a unique asynchronous timing metronome device specific to the physiologic needs of human subjects as defined by a breathing definition and training method, by controlling respiratory rate and the relative times of inspiration and expiration.
It is another object of the present invention to provide simple visual and/or auditory prompting signals to patients to accurately activate desirable native breathing patterns and learned breathing patterns.
It is yet another object of the present invention to provide breathing control signals to control excessive ventilation, and thereby prevent or reverse Hyperventilation Syndrome adverse consequences.
It is still another object of the present invention to provide breathing control signals to prevent or correct Dynamic Hyperinflation in Asthma and Emphysema.
It is further object of the present invention to provide a portable, battery operated device suitable for operation in the field.
It is still further object of the present invention to optionally provide a device suitable for operating in adverse environments such as underwater diving conditions.
It is a final objective of the present invention to optionally provide a manual override control to prolong the expiratory time by 25% while simultaneously causing the expiratory auditory and visual signals to be continuous, to promote both respiratory rate slowing and deflation of overinflated lungs.
These objectives are achieved by training with a sophisticated visual and auditory biofeedback training device, and in the field by a portable, battery operated device which mimics the learned inspiration and expiration timing. Optionally this is achieved with two types of display. In the simplest form visual prompting is by one Light Emitting Diode (LED) of differing color, one for inspiration and the other for expiration. Optionally the auditory component may be activated, with a simple xe2x80x9cbeep (high pitched)xe2x80x9d or xe2x80x9ctickxe2x80x9d sound indicating inspiration and a xe2x80x9cbeep (low pitched)xe2x80x9d or xe2x80x9ctockxe2x80x9d sound indicating expiration. In another preferred embodiment there is one LED to indicate inspiration and another LED to indicate expiration.
Both models of the invention have similar function controls, one to set respiratory rate, and the other to then independently set the time ratio between inspiration and expiration. In the normal subject this Inspiration:Expiration Ratio is typically 1:1.4, and in Emphysema patients and others it typically must be set to 1:1.7 or longer, for example 1:2.5. Otherwise the controls are identical with a system on/off switch, sound on/off switch, a sound volume adjustment control, and a manual expiration prolongation override button.